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Systemic mastocytosis (SM) is a clonal mast cell disorder that can lead to potentially severe anaphylactic reactions. Hymenoptera sting is one of the most frequent triggers of anaphylaxis in these patients, and diagnosis of indolent SM (ISM) without skin involvement (ISMs) is not rare. In this subgroup of patients, venom immunotherapy (VIT) is an effective treatment decreasing subsequent systemic reactions, and lifelong administration is recommended. An individualized diagnosis is necessary to offer the most adequate VIT, and molecular diagnosis (MD) may be useful to discriminate between primary sensitization and cross-reactivity. Nevertheless, other techniques such as ImmunoCAP inhibition assays may be necessary to identify the genuine sensitization to offer the most suitable VIT. We present a male patient with an anaphylactic reaction following several wasp stings. The patient was diagnosed with ISM, and allergy to both Polistes dominula and Vespula sp venom was confirmed. In this scenario, MD did not discriminate between a genuine double sensitization and venom cross-reactivity between both vespids. Thus, CAP-inhibition assay was performed. This case indicated the importance of an accurate diagnosis of hymenoptera venom allergy (HVA). It also highlights the usefulness of CAP-inhibition assays when MD fails to distinguish between genuine double Polistes-Vespula sensitization and cross-reactivity., Competing Interests: The authors declare no potential conflicts of interest with respect to research, authorship, and/or publication of this article.

Background: Patients with mastocytosis and wasp venom allergy (WA) may benefit from venom immunotherapy (VIT). However, fatal insect sting reactions have been described in mastocytosis patients despite previous immunotherapy. We investigated the safety and efficacy of (rush) VIT in patients with mastocytosis and WA., Objective: To investigate the safety and efficacy of (rush) VIT in patients with mastocytosis and WA., Methods: We describe nine patients with cutaneous mastocytosis and WA who received VIT. Cutaneous mastocytosis was confirmed by histopathology and systemic mastocytosis was diagnosed according to World Health Organization criteria. VIT was given according to a rush protocol. Given the difference in safety and efficacy of VIT in patients with WA and honeybee venom allergy, we reviewed the literature for VIT with the focus on WA patients with mastocytosis and addressed the difference between patients with cutaneous versus systemic mastocytosis., Results: Nine patients had WA and mastocytosis, of whom six had cutaneous mastocytosis, two combined cutaneous and systemic mastocytosis and one systemic mastocytosis. All patients received rush IT with wasp venom. Most patients had only mild local side effects, with no systemic side effects during the course of VIT. One patient had a systemic reaction upon injection on one occasion, during the updosing phase, with dyspnoea and hypotension, but responded well to treatment. Immunotherapy was continued after temporary dose adjustment without problems. Two patients with a previous anaphylactic reaction were re-stung, without any systemic effects., Conclusions: VIT is safe in cutaneous mastocytosis patients with WA, while caution has to be made in case of systemic mastocytosis. VIT was effective in the patients who were re-stung.

A 47-year-old man presented with loss of consciousness 5 minutes after being stung by a yellow jacket in his backyard. Epinephrine and fluids were required for resuscitation. Allergy evaluation revealed specific IgE to yellow jacket and honeybee, and the patient was started on venom immunotherapy. He had systemic reactions during buildup and a severe anaphylactic episode requiring 3 doses of intramuscular epinephrine at maintenance doses. Immunotherapy was discontinued. Serum tryptase level after 1 such episode was 29 ng/mL, with a baseline level of 25 ng/mL 4 weeks later. The physical examination was unremarkable including no skin lesions of cutaneous mastocytosis. Because of elevated baseline tryptase level, a bone marrow biopsy was performed, which revealed multifocal dense infiltrates of mast cells. A diagnosis of systemic mastocytosis was made. The patient was treated with omalizumab and was able to tolerate immunotherapy and is currently maintained on lifelong immunotherapy. He was restung in the field and has not had anaphylaxis., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)